A. Field of The Invention
The present invention relates to recombinant DNA technology. It is especially useful for allowing stable replication of foreign eukaryotic genes in eukaryotic hosts.
B. Description of The Art
Although much progress has been made in the last decade in using recombinant-DNA techniques with prokaryotic hosts, many important eukaryotic proteins (e.g. plasminogen activator) are not readily expressed in a prokaryotic host. It therefore is desirable to develop recombinant vectors for use with eukaryotic hosts.
Using plasmids as vectors for eukaryotic hosts has been tried, but with only limited success. For example, the SV-40 vector in R. C. Mulligan et al., 78. P.N.A.S. U.S.A. 2072-6 (1981) either replicated too fast and killed the cell or integrated into the cell genome (which led to loss of expression, mutation, and other problems). Some bovine papilloma virus plasmid vectors have also been tried, see ATCC Quarterly News Letter (July 1984), but they have had very limited host ranges (and thus are of very limited commercial value). Thus, it can be seen that there is a need for an improved vector that permits stable replication of eukaryotic DNA in a wide range of hosts.